(function(){
  var crypt = require('crypt'),
      utf8 = require('charenc').utf8,
      isBuffer = require('is-buffer'),
      bin = require('charenc').bin,

  // The core
  md5 = function (message, options) {
    // Convert to byte array
    if (message.constructor == String)
      if (options && options.encoding === 'binary')
        message = bin.stringToBytes(message);
      else
        message = utf8.stringToBytes(message);
    else if (isBuffer(message))
      message = Array.prototype.slice.call(message, 0);
    else if (!Array.isArray(message) && message.constructor !== Uint8Array)
      message = message.toString();
    // else, assume byte array already

    var m = crypt.bytesToWords(message),
        l = message.length * 8,
        a =  1732584193,
        b = -271733879,
        c = -1732584194,
        d =  271733878;

    // Swap endian
    for (var i = 0; i < m.length; i++) {
      m[i] = ((m[i] <<  8) | (m[i] >>> 24)) & 0x00FF00FF |
             ((m[i] << 24) | (m[i] >>>  8)) & 0xFF00FF00;
    }

    // Padding
    m[l >>> 5] |= 0x80 << (l % 32);
    m[(((l + 64) >>> 9) << 4) + 14] = l;

    // Method shortcuts
    var FF = md5._ff,
        GG = md5._gg,
        HH = md5._hh,
        II = md5._ii;

    for (var i = 0; i < m.length; i += 16) {

      var aa = a,
          bb = b,
          cc = c,
          dd = d;

      a = FF(a, b, c, d, m[i+ 0],  7, -680876936);
      d = FF(d, a, b, c, m[i+ 1], 12, -389564586);
      c = FF(c, d, a, b, m[i+ 2], 17,  606105819);
      b = FF(b, c, d, a, m[i+ 3], 22, -1044525330);
      a = FF(a, b, c, d, m[i+ 4],  7, -176418897);
      d = FF(d, a, b, c, m[i+ 5], 12,  1200080426);
      c = FF(c, d, a, b, m[i+ 6], 17, -1473231341);
      b = FF(b, c, d, a, m[i+ 7], 22, -45705983);
      a = FF(a, b, c, d, m[i+ 8],  7,  1770035416);
      d = FF(d, a, b, c, m[i+ 9], 12, -1958414417);
      c = FF(c, d, a, b, m[i+10], 17, -42063);
      b = FF(b, c, d, a, m[i+11], 22, -1990404162);
      a = FF(a, b, c, d, m[i+12],  7,  1804603682);
      d = FF(d, a, b, c, m[i+13], 12, -40341101);
      c = FF(c, d, a, b, m[i+14], 17, -1502002290);
      b = FF(b, c, d, a, m[i+15], 22,  1236535329);

      a = GG(a, b, c, d, m[i+ 1],  5, -165796510);
      d = GG(d, a, b, c, m[i+ 6],  9, -1069501632);
      c = GG(c, d, a, b, m[i+11], 14,  643717713);
      b = GG(b, c, d, a, m[i+ 0], 20, -373897302);
      a = GG(a, b, c, d, m[i+ 5],  5, -701558691);
      d = GG(d, a, b, c, m[i+10],  9,  38016083);
      c = GG(c, d, a, b, m[i+15], 14, -660478335);
      b = GG(b, c, d, a, m[i+ 4], 20, -405537848);
      a = GG(a, b, c, d, m[i+ 9],  5,  568446438);
      d = GG(d, a, b, c, m[i+14],  9, -1019803690);
      c = GG(c, d, a, b, m[i+ 3], 14, -187363961);
      b = GG(b, c, d, a, m[i+ 8], 20,  1163531501);
      a = GG(a, b, c, d, m[i+13],  5, -1444681467);
      d = GG(d, a, b, c, m[i+ 2],  9, -51403784);
      c = GG(c, d, a, b, m[i+ 7], 14,  1735328473);
      b = GG(b, c, d, a, m[i+12], 20, -1926607734);

      a = HH(a, b, c, d, m[i+ 5],  4, -378558);
      d = HH(d, a, b, c, m[i+ 8], 11, -2022574463);
      c = HH(c, d, a, b, m[i+11], 16,  1839030562);
      b = HH(b, c, d, a, m[i+14], 23, -35309556);
      a = HH(a, b, c, d, m[i+ 1],  4, -1530992060);
      d = HH(d, a, b, c, m[i+ 4], 11,  1272893353);
      c = HH(c, d, a, b, m[i+ 7], 16, -155497632);
      b = HH(b, c, d, a, m[i+10], 23, -1094730640);
      a = HH(a, b, c, d, m[i+13],  4,  681279174);
      d = HH(d, a, b, c, m[i+ 0], 11, -358537222);
      c = HH(c, d, a, b, m[i+ 3], 16, -722521979);
      b = HH(b, c, d, a, m[i+ 6], 23,  76029189);
      a = HH(a, b, c, d, m[i+ 9],  4, -640364487);
      d = HH(d, a, b, c, m[i+12], 11, -421815835);
      c = HH(c, d, a, b, m[i+15], 16,  530742520);
      b = HH(b, c, d, a, m[i+ 2], 23, -995338651);

      a = II(a, b, c, d, m[i+ 0],  6, -198630844);
      d = II(d, a, b, c, m[i+ 7], 10,  1126891415);
      c = II(c, d, a, b, m[i+14], 15, -1416354905);
      b = II(b, c, d, a, m[i+ 5], 21, -57434055);
      a = II(a, b, c, d, m[i+12],  6,  1700485571);
      d = II(d, a, b, c, m[i+ 3], 10, -1894986606);
      c = II(c, d, a, b, m[i+10], 15, -1051523);
      b = II(b, c, d, a, m[i+ 1], 21, -2054922799);
      a = II(a, b, c, d, m[i+ 8],  6,  1873313359);
      d = II(d, a, b, c, m[i+15], 10, -30611744);
      c = II(c, d, a, b, m[i+ 6], 15, -1560198380);
      b = II(b, c, d, a, m[i+13], 21,  1309151649);
      a = II(a, b, c, d, m[i+ 4],  6, -145523070);
      d = II(d, a, b, c, m[i+11], 10, -1120210379);
      c = II(c, d, a, b, m[i+ 2], 15,  718787259);
      b = II(b, c, d, a, m[i+ 9], 21, -343485551);

      a = (a + aa) >>> 0;
      b = (b + bb) >>> 0;
      c = (c + cc) >>> 0;
      d = (d + dd) >>> 0;
    }

    return crypt.endian([a, b, c, d]);
  };

  // Auxiliary functions
  md5._ff  = function (a, b, c, d, x, s, t) {
    var n = a + (b & c | ~b & d) + (x >>> 0) + t;
    return ((n << s) | (n >>> (32 - s))) + b;
  };
  md5._gg  = function (a, b, c, d, x, s, t) {
    var n = a + (b & d | c & ~d) + (x >>> 0) + t;
    return ((n << s) | (n >>> (32 - s))) + b;
  };
  md5._hh  = function (a, b, c, d, x, s, t) {
    var n = a + (b ^ c ^ d) + (x >>> 0) + t;
    return ((n << s) | (n >>> (32 - s))) + b;
  };
  md5._ii  = function (a, b, c, d, x, s, t) {
    var n = a + (c ^ (b | ~d)) + (x >>> 0) + t;
    return ((n << s) | (n >>> (32 - s))) + b;
  };

  // Package private blocksize
  md5._blocksize = 16;
  md5._digestsize = 16;

  module.exports = function (message, options) {
    if (message === undefined || message === null)
      throw new Error('Illegal argument ' + message);

    var digestbytes = crypt.wordsToBytes(md5(message, options));
    return options && options.asBytes ? digestbytes :
        options && options.asString ? bin.bytesToString(digestbytes) :
        crypt.bytesToHex(digestbytes);
  };

})();
